| From: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
|---|---|
| To: | Gurjeet Singh <singh(dot)gurjeet(at)gmail(dot)com> |
| Cc: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>, Terry Lee Tucker <terry(at)chosen-ones(dot)org>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: LIMIT Question |
| Date: | 2008-02-29 10:25:41 |
| Message-ID: | 20080229102541.GA28668@svana.org |
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| Thread: | |
| Lists: | pgsql-general |
On Fri, Feb 29, 2008 at 02:53:05PM +0530, Gurjeet Singh wrote:
> In my opinion (without looking at the code), if you have a grouping-function
> or ORDER BY or GROUP BY clause, then yes, the whole query has to be executed
> to show the first row of the result-set. But if the query doesn't have any
> of these clauses, then the DB has the ability to send back the first row
> from the result as soon as it processes it (i.e after WHERE clause
> processing), and stop the query execution there.
Except if you have an index on the column you're ordering by. Then the
server can really return the first row quickly.
Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Those who make peaceful revolution impossible will make violent revolution inevitable.
> -- John F Kennedy
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